On the nature and timing of oxygen radical production following exposure ofArabidopsis thalianaleaves to uranium, cadmium or a combination of both stressors

Abstract

The toxicity and oxidative stress responses of 19-day old Arabidopsis seedlings induced by U (66 M) and Cd (20 M) alone or in a binary mixture set-up (equitoxic mixture) are studied in function of time. After 48h a significant decrease in root and shoot growth and a simultaneous increase in anthocyanin production was evident in all treated plants. Production of O .− 2 or H 2 O 2 was visualized by staining freshly harvested leaves with nitrobluetetrazolium or diaminobezidine, respectively. With this method production of O .− 2 was only significantly measurable after 168 h treatment which coincides with a significant decrease in biomass production and probably also plant cell death. For Cd treated plants a significant increase in H 2 O 2 production was measurable from 24h onwards. In contrast, a similar H 2 O 2 production could not be measured in U or U + Cd treated plants. Both water and lipophilic soluble antioxidants significantly increased in U treated plants after 48 h. These high antioxidant levels might detoxify potential H 2 O 2 produced in the U treated plants. In contrast for Cd treated plants only after 168h a significant increase in water soluble antioxidants was measured whereas no difference in the lipophilic fraction was visible.

Oxidative stress responses induced by uranium exposure at low pH in leaves of Arabidopsis thaliana plants

“…They reported an EC50 value of 66 mM U for leaf growth reduction of A. thaliana plants exposed to U during 3 days at pH 5.5. Since the EC50 value we found is about 2.3 times lower than the value reported by Horemans et al (2011), this can indicate that U induces more toxic effects at low pH. Similar results were reported before by Saenen et al (2013), where a decreased fresh weight, an increased dry weight, increased lipid peroxidation and activation of antioxidative enzymes were mainly observed at pH 4.5, indicating that U effects were more severe at low pH, i.e.…”

“…The EC50 value from the present experiment (27.13 ± 5.20 mM U) is remarkably lower than the EC50 value observed before by Horemans et al (2011). They reported an EC50 value of 66 mM U for leaf growth reduction of A. thaliana plants exposed to U during 3 days at pH 5.5.…”

Induction of Oxidative Stress and Antioxidative Mechanisms in Arabidopsis thaliana after Uranium Exposure at pH 7.5

“…Despite the low U concentrations in the leaves, a significant decrease in leaf fresh weight was observed ( Figure 2 ). The EC50 (53.74 ± 3.51 µM U) is comparable to the EC50 observed by Horemans et al [ 35 ] for leaf growth reduction after U exposure at pH 5.5. They observed an EC50 value of 66 µM U.…”

Effects of pH on uranium uptake and oxidative stress responses induced in Arabidopsis thaliana

“…This can have an impact on U uptake and translocation . So far, most research on A. thaliana has been carried out under standard conditions with a growth medium of pH 5.0 to pH 5.7 . However, the pH of porewater varies naturally.…”